Toll fraud eliminator for telephone systems

• US 4,002,848 A
• Filed: 09/26/1975
• Issued: 01/11/1977
• Est. Priority Date: 11/14/1974
• Status: Expired due to Term

• Current Assignee: Reliable Electric Company
• Original Assignee: Reliable Electric Company
• Inventors: Stein, Richard P.
• Primary Examiner(s): Brown, Thomas W.
• Application Number:
  US05/617,188
• Time in Patent Office: 473 Days
• Field of Search: 179/18 DA, 179/27 CB, 179/84 VF
• US Class Current: 379/119
• CPC Class Codes: H04M 15/04 Recording calls , or communications in printed, perforated or other permanent form
• CPC Class Codes: H04Q 1/444 with voice-band signalling frequencies

Abstract

A tone detector is connected or otherwise associated with an outgoing telephone trunk line adapted to be included in a toll path. One or more frequency or tone signals are sent over the trunk line for signaling and control during a toll call. If these tone signals appear at a point on the trunk line where the toll call remains under the control of d.c. signals, they must be fraudulent since there is no preceding equipment which is adapted to send valid tone signals. Therefore, a tone detector may be connected to that point in order to drop or otherwise block any calls during which the fraudulent tone signals appear. The toll fraud eliminator is particularly -- but not exclusively -- useful for preventing employment of a "blue box" during toll calls. The tone detector uses two multivibrators which operate at an upper and a lower threshold frequency respectively. The half cycles of a given polarity in the single frequency tone must recur fast enough to continuously reset the multivibrator running at the lower threshold frequency, but not fast enough to continuously reset the multivibrator running at the upper threshold frequency.

Claims

1. A system including a single frequency toll fraud eliminator, said system comprising a telephone exchange having a plurality of lines connected to one side and trunks connected to the other side, at least one of said trunks comprising a d.c. to single frequency converter means connected to originate and terminate ends of said one trunk;

said toll fraud eliminator comprising single frequency tone detecting means connected to said one trunk on the d.c. side of said d.c. to single frequency converter means at the end of said one trunk where said call originated, whereby said tone detector is connected into said trunk at a point where an apparently valid control tone signal of said single frequency cannot legitimately appear, said single frequency tone detecting means operating responsive to signals having said single frequency and call barring means operated responsive to said single frequency tone detecting means for interrupting any call connection from said exchange which is then using said telecommunication channel.

2. The fraud eliminator of claim 1 wherein said give frequency is a 2600 Hz tone.

3. A fraud eliminator comprising means for connecting said eliminator into a telecommunication channel at a point where an apparently valid control tone signal of a given frequency cannot legitimately appear, fraudulent tone detector means in said eliminator operated responsive to signals having said given frequency of an apparently valid control tone signal, call barring means operated responsive to said fraudulent tone detector means detecting said apparently valid control tone for interrupting any call connection then using said telecommunication channel, a pair of timing means for respectively measuring two distinctive time periods corresponding to upper and lower frequency thresholds on either side of said given frequency, means responsive to an appearance of a tone on said line for continuously retriggering said timing means at the frequency of said tone, and means responsive to a continued retriggering of the timing means for measuring said lower threshold and to a non-retriggering of timing means for measuring said upper threshold for signaling the presence of the tone.

4. The fraud eliminator of claim 3 wherein each of said pair of timing means is a one shot multi-vibrator.

5. The fraud eliminator of claim 3 and means for measuring a predetermined period of apparently valid tone before signaling the presence of the tone, said predetermined period being approximately 0.13 seconds.

6. A toll fraud eliminator for connection to a path extending from a telephone line through a central telephone office switch train to a trunk line, comprising means for connecting said fraud eliminator between said switch train and said trunk line while said path is part of a connection between two subscribers, toll ticketing means for registering toll charges relating to calls made between subscribers, signal generating means connected between said fraud eliminator and said trunk line for producing a signal tone of predetermined frequency on said trunk line, and switch means connected between said signal generating means and said switch train and operated responsive to an appearance of said signal tone at a point between said signal generating means and said switch train for automatically disconnecting said subscribers to prevent toll fraud.

7. The toll fraud eliminator of claim 6 wherein said toll ticketing means is operated responsive to an appearance of a tone generated by said signal generating means and the operation is canceled responsive to said switch means.

8. A toll fraud eliminator for connection into a telephone line, comprising means for connecting said fraud eliminator to said line while it is part of a connection between two subscribers, said line including toll ticketing means for registering toll charges relating to calls made between subscribers, signal generating means connected downstream from one of said subscribers for producing a signal tone of predetermined frequency, said toll ticketing means being operated responsive to an appearance of a tone generated by said signal generating means, switch means connected to said telephone line upstream from said signal generating means and operated responsive to an appearance of said signal tone at said upstream connection for automatically disconnecting said subscribers to prevent toll fraud, the operation of said toll ticketing means being canceled responsive to said switch means, a pair of timing means for respectively measuring two distinctive time periods corresponding to upper and lower frequency thresholds on either side of said signal tone frequency, said switch means comprising circuit means responsive to an appearance of a tone on said line for continuously retriggering said timing means at the frequency of said tone, and means responsive to a continuous retriggering of the timing means measuring said lower threshold and to a non-retriggering of the timing means measuring said upper threshold for signaling the presence of the tone.

9. The toll fraud eliminator of claim 8 wherein each of said pair of timing means is a one shot multi-vibrator.

10. A toll fraud eliminator for connection into a telephone line, comprising means for connecting said fraud eliminator to said line while it is part of a connection between two subscribers, said line including toll ticketing means for registering toll charges relating to calls made between subscribers, signal generating means connected downstream from one of said subscribers for producing a signal tone of predetermined frequency, switch means connected to said telephone line upstream from said signal generting means and operated responsive to an appearance of said signal tone at said upstream connection for automatically disconnecting said subscribers to prevent toll fraud, said toll ticketing means being operated responsive to an appearance of a tone generated by said signal generating means, said operation being canceled responsive to disconnect by said switch means, and circuit means responsive to the output of said switch means for measuring the duration of said signal tone for at least a predetermined time period prior to said disconnection of said subscribers when signals of said predetermined signal tone frequency are applied to the telephone line location, whereby the cancellation of the operation of said toll ticketing means and the automatic disconnection of said subscribers occurs only after said predetermined time period.

11. A toll fraud eliminator for use on a toll path including at least one telecommunication channel, comprising a d.c. to single frequency converter means connected to originate and terminate ends of said telecommunication channel;

said toll fraud eliminator comprising means for connecting said eliminator to said toll path on the d.c. side of said d.c. to single frequency converter means at the originating end of said telecommunication channel, means responsive to signals appearing on said connecting means for precluding a continuation of a call or an attempted call in progress when said signals so appear, said call continuation precluding means comprising means for detecting upper and lower threshold frequencies on opposite sides of said single frequency connected in a series circuit including a relay, said threshold detecting means passing substantially only said single frequency, means responsive to the output of said threshold detecting means for operating said relay, and contacts on said relay for causing said preclusion of the continuation of said telephone call.

12. The toll fraud eliminator of claim 11 and means associated with said threshold detecting means comprising a duration timing means for precluding operation of said relay until after the elapse of an initial period following an output from said threshold detection means.

13. The toll fraud eliminator of claim 12 wherein said threshold detecting means comprises a pair of timing means for respectively measuring two distinctive time periods corresponding to said upper and lower threshold frequencies, means responsive to an appearance of said single frequency on said d.c. side of said single frequency converter means at said originating end for continuously retriggering said timing means at the single frequency, and means responsive to a continuous retriggering of the timing means measuring said lower threshold and to a non-retriggering of timing means measuring said upper threshold for signaling the presence of the single frequency.